Overview

The TD06H-20G turbocharger is a popular upgrade for the Subaru WRX, offering a significant boost in horsepower and torque over the stock unit. This guide provides a detailed, step-by-step approach to installing the TD06H-20G on your WRX safely and effectively. Whether you are a seasoned mechanic or an ambitious DIY enthusiast, following these instructions will help you achieve a reliable and powerful turbo upgrade. Always prioritize safety, use the correct tools, and consult your vehicle’s service manual for specific torque values and procedures. For additional reference, review resources from trusted sources such as Import Image Racing and Subaru’s official owner portal.

Tools and Materials Needed

Before beginning, gather all necessary tools and components. Having everything on hand will streamline the installation and minimize downtime.

  • TD06H-20G turbocharger assembly (including wastegate actuator if separate)
  • Socket set (metric: 10mm, 12mm, 14mm, 17mm, 19mm)
  • Combination wrenches (10mm, 12mm, 14mm, 17mm)
  • Screwdrivers (flathead and Phillips)
  • Torque wrench (range 10–150 ft-lb)
  • Gasket scraper / razor blade
  • New gaskets: turbo-to-manifold, turbo-to-downpipe, intake-to-turbo, oil return, coolant flange
  • Oil feed line (braided stainless or OEM replacement with restrictor, as needed)
  • Oil drain line (new hose or OEM with new gaskets)
  • Intercooler piping kit (Y-pipe, couplers, and T-bolt clamps)
  • Coolant hoses (upper and lower, with new spring clamps)
  • Vacuum hose (various sizes for boost reference and wastegate)
  • High-temperature silicone sealant (for gasket mating surfaces if recommended)
  • Shop towels, brake cleaner, and rags
  • Penetrating oil (e.g., PB Blaster) for stubborn bolts
  • Safety glasses and mechanic gloves

Preparation and Safety

Park the vehicle on a level surface and allow the engine to cool completely. Disconnect the negative battery terminal to prevent accidental starting or short circuits. Raise the front of the car using jack stands (never rely on a jack alone) and remove the under-engine splash shield if equipped. Work in a well-ventilated area, and keep a fire extinguisher nearby as a precaution. Take photos or label connections before disassembly to aid reassembly.

Step 1: Remove the Stock Turbocharger

1.1 Remove Intake and Intercooler

Loosen the clamps on the intake duct from the air filter box to the turbo. Disconnect the Mass Air Flow (MAF) sensor connector and remove the intake duct. Next, unbolt the intercooler, typically secured by four 12mm bolts, and disconnect the Y-pipe from the throttle body and turbo compressor outlet. Slide the intercooler upward and out of the engine bay.

1.2 Access the Turbocharger

Remove the turbo heat shield (three 10mm bolts). Disconnect the oil feed line from the block and the turbo using a 12mm or 14mm wrench. Disconnect the oil drain hose from the bottom of the turbo and the block fitting (usually a 14mm banjo bolt). Drain the coolant by disconnecting the upper and lower coolant hoses at the turbo. Have a drain pan ready for residual fluid.

1.3 Unbolt and Remove Stock Turbo

Using penetrating oil on the turbo-to-manifold and turbo-to-downpipe bolts, let it soak for a few minutes. Unbolt the downpipe from the turbo (four 14mm nuts). Support the turbo with one hand, then remove the four 14mm nuts securing it to the exhaust manifold. Carefully lower the turbo and remove it from the engine bay. Inspect the manifold surface for cracks or warping.

Step 2: Prepare the New TD06H-20G Turbocharger

Clean the exhaust manifold flange and the downpipe flange using a gasket scraper and brake cleaner. Ensure all old gasket material is removed. Inspect the new TD06H-20G turbo for any damage during shipping. Verify that the oil feed and drain ports are clean and free of debris. Install the supplied gasket on the manifold side of the turbo, ensuring proper orientation. If the TD06H-20G does not include an internal wastegate actuator, install the external wastegate and align the flapper valve correctly.

Step 3: Install the TD06H-20G Turbocharger

3.1 Mount the Turbo to the Manifold

Carefully position the new turbo onto the exhaust manifold studs. The turbine housing should sit flush with the manifold. Hand-thread the four 14mm nuts onto the studs. Use a torque wrench to tighten them in a crisscross pattern to the manufacturer’s specification (typically 35–40 ft-lb for Subaru). Do not overtighten, as exhaust manifold studs can snap.

3.2 Reattach the Downpipe

Install a new gasket between the turbo outlet and downpipe. Align the downpipe and hand-thread the nuts. Tighten to 35 ft-lb in a diagonal pattern. Inspect the downpipe for clearance with the turbo housing; you may need to adjust or modify the downpipe for the larger TD06H-20G housing.

Step 4: Connect Oil and Coolant Lines

4.1 Oil Feed Line

Connect the oil feed line to the turbo using a new crush washer (if applicable). For TD06H-20G turbos, a restrictor in the oil feed may be required to control oil flow—check the manufacturer’s instructions. Tighten the banjo bolt to 25–30 ft-lb. Secure the line away from exhaust components with zip ties.

4.2 Oil Drain Line

Attach the oil drain hose to the turbo’s bottom outlet and the block fitting. Use a new gasket on the block flange. Ensure the drain line has a constant downward slope to allow gravity-assisted oil return. Tighten bolts to 12–15 ft-lb.

4.3 Coolant Lines

Reconnect the upper and lower coolant hoses to the turbo-specific ports. Use new spring clamps or worm-gear clamps, and tighten securely. After installation, the coolant system will need to be bled to remove air pockets.

Step 5: Reinstall the Intercooler and Intake System

Reinstall the intercooler, ensuring the Y-pipe aligns with the TD06H-20G compressor outlet. The larger turbo may require a modified or relocated intercooler piping kit. Use T-bolt clamps for boost retention. Reattach the air intake duct, ensuring the MAF sensor is properly seated and the connector is locked. Tighten all clamps to prevent boost leaks.

Step 6: Reconnect Vacuum Lines and Wastegate

Route a new vacuum line from the wastegate actuator (or external wastegate) to a boost source, such as the compressor cover or a dedicated boost controller. Use silicone vacuum hose rated for high heat. Double-check that the wastegate linkage moves freely and is not binding against any part of the engine bay.

Step 7: Final Checks and Fluid Top-Up

Inspect all connections for tightness: turbo mounting nuts, downpipe nuts, oil lines, coolant hoses, and intercooler clamps. Refill engine oil to the proper level. Refill coolant and bleed the system by running the engine with the radiator cap off until the thermostat opens and bubbles stop. Reconnect the battery. Start the engine and let it idle. Check for oil or coolant leaks immediately. Listen for any unusual noises from the turbo, such as scraping or excessive whining.

Step 8: Test Drive and Tuning Considerations

Once leaks are confirmed absent, take the vehicle for a gentle test drive. Monitor boost pressure via a gauge—the TD06H-20G typically produces 14–18 psi on a stock WRX engine with proper supporting mods and tuning. Avoid sustained full-throttle runs until you have a professional ECU tune. Upgrading the turbo without recalibrating the fuel and ignition maps risks engine damage. It is highly recommended to install a wideband O2 sensor and use a reputable tuner. Resources like Cobb Tuning offer Accessport tuning solutions that can be customized for the TD06H-20G setup.

Post-Installation Troubleshooting

  • Oil leaks: Check that the oil feed restrictor is correctly sized; too much oil pressure can cause seal failure.
  • Boost creep: The larger turbine housing may require a boost controller or porting to maintain target boost.
  • Check engine light: May indicate a vacuum leak, MAF issue, or insufficient tune—scan codes and address promptly.
  • Excessive smoke: Could be oil entering the exhaust from a leaking turbo seal or overfilled crankcase; check drain line slope.

Conclusion

Installing the TD06H-20G turbocharger on your Subaru WRX is a substantial upgrade that transforms the car’s performance when done correctly. By meticulously following this step-by-step guide, using quality components, and investing in professional tuning, you can enjoy a reliable and powerful setup that stands up to track days and spirited driving. Always adhere to safety practices and consult the manufacturer’s instructions for your specific turbo model. For further reading, NASIOC forums are a valuable community resource for troubleshooting and tuning advice.